When a dog or similar size / type of animal clamps onto a human's leg, and gives your leg a good fucking, usuallywithout the human's consent.

Lewy walked into room with Jim, with Jim asking Lewy, "Where is your dog?" Within a second of hearing Lewy's voice, Woody the dog of the house clamped onto Lewy's leg. Lewy then being pushed to the floor as Woody fucked his leg good and hard.